Southerlyn often disagreed with McCoy over their trial strategies in cases where she sees the defendant's crime as a by-product of social circumstances, such as homelessness or racism. She had an especially troubled relationship with Branch, a conservative who replaced Lewin as District Attorney in 2002.
In the 2002 episode "DR 1-102", Southerlyn is brought before the New York Supreme Court, Appellate Division's Disciplinary Committee after promising to get legal help for a murder suspect who had taken hostages, to get him to release his prisoners. The man had a knife to a woman's throat and demanded a lawyer. Southerlyn, who happened to be in the area, volunteered to enter the store where the holdup was taking place, to negotiate the hostage's release. Since the man had asked for a lawyer, the committee attempts to paint Southerlyn's actions as fraudulent, since she was supposedly representing herself as his lawyer (which she denies), when she was in fact a district attorney. McCoy, who had been brought before the committee himself in the 1998 episode "Monster", represents her. She is reprimanded, but keeps her law license.
In several episodes, Southerlyn is portrayed as opposing the death penalty, which often puts her in a difficult ethical position when working with McCoy and Branch, who both support capital punishment.
Röhm left the show in the middle of the fifteenth season, and made her last appearance in the episode "Ain't No Love." She was replaced by Alexandra Borgia (Annie Parisse).
Her departure was noteworthy due to a surprising conversation between Southerlyn and Branch in the very last scene of the episode. At the close of the show, Branch dismisses Southerlyn because he feels she is too sympathetic toward defendants, and that her emotions get in the way of looking at the facts. A stunned Southerlyn pauses for a moment, then asks, "Is this because I'm a lesbian?" Taken aback by the accusation, Branch protests, "No. Of course not. No." Her final line is "Good.... Good." This is the first and only instance that Southerlyn's homosexuality was ever explicitly mentioned, although there had been subtle hints in earlier episodes. In the 2004 episode "Gov Love," she is uncomfortable with a case in which McCoy successfully seeks to have same-sex marriage declared illegal in New York in order to get testimony from a gay defendant's spouse. Southerlyn had objected to this and refused to assist McCoy, but her sexual orientation was never mentioned.
She mentions in another episode that she dated a male college student while she was still in high school and that he is now a New York State Senator.
The decision to announce Southerlyn's homosexuality only as the character left the show was widely denounced both by fans and critics.Slate's Dana Stevens called the line "a cheap stunt", as did USA Today's Robert Bianco and numerous fans. The media director for the Gay & Lesbian Alliance Against Defamation (GLAAD) stated to Chicago Tribune television critic Maureen Ryan, "For a show that usually employs gay and lesbian characters as sensational plot devices, it's really disappointing to have one of the leads come out five seconds before she exits the show," and Ryan cited as "typical" a fan comment from Universal Television's fan forum that read, "They have never discussed her sexuality on the show before and all of a sudden, she's gay in her last two lines? Terrible writing decision." Tim Goodman of the San Francisco Chronicle joined those calling the move a "cheap stunt", adding, "but here's why it didn't work: Anyone who knows anything about gay people knows that no lesbian could ever be that bad of an actress." Diane Holloway of the Austin American-Statesman was one of many critics who chose to answer Southerlyn's on-screen question, while citing her as third runner-up for a list of "the most annoying actors on television".
Gone and almost forgotten, but destined to live on in endless reruns on TNT. This wide-eyed 'actress' with the tedious monotone nearly ruined one of my favorite series, stumbling through cue cards and generally not acting as Assistant District Attorney Southerlyn for four seasons. Her final line upon getting fired was the only memorable one of her career: 'Is it because I'm a lesbian?' No, Ms. Rohm. It's because you have no talent. 
Critic Kevin Thompson of the Palm Beach Post similarly replied, "No, it's because you're a robotic actress."
Series creator Dick Wolf later explained at the Television Critics Association press tour that he had consulted Röhm before scripting the scene — the only Wolf-authored scene in the installment — saying, "Do you want to go out with a bang or a whimper?" He characterized the scene as "unabashedly a water-cooler moment. And the fact that we're discussing it shows that I think it worked as a water-cooler moment." Wolf also noted the effectiveness of the device by reporting that the show's main online chat room "crashed 15 minutes after the show was over," although critic Alan Pergament joked in his column that the response came not because viewers approved, but "because many fans thought the out-of-left field ending was a crime."
TV Guide called Rohm "arguably the most inept cast member" in the series' first 18 years, with Ben Katner writing "we are dancing in the streets" upon her departure. Dusin Rowles of Pajiba described Rohm as a "disaster" and a "catastrophe".Entertainment Weekly called Rohm's performance and character "wooden".AfterEllen.com reported that Southerlyn was "one of the show's more disliked characters" due to her "cold and robotic" portrayal.
^ abKate Aurthur and Lawrence Van Gelder. "Battling crime shows" (TV ratings column), The New York Times, January 15, 2005, Section: The Arts, page 8: "Wednesday's episode featured the departure of Elisabeth Rohm ... as an assistant district attorney. 'Is this because I'm a lesbian?' she asked as she was being fired, much to the surprise of viewers, who have been shown little about the characters' personal lives."
^"Ain't No Love". Law & Order. Season 15. Episode 13. January 12, 2005. NBC.
^Virginia Rohan. "'Law & Order' 'outs' its token lesbian," The Record (Hackensack, NJ), January 17, 2005, page F02.
^Dusty Saunders. "'L&O' ending jolts even star," Rocky Mountain News (CO), January 17, 2005, page 2D.
^ abDana Stevens. "Prelude to a kiss," Slate, January 17, 2005.
^ abRobert Bianco. "Critic's corner," USA Today (Arlington, VA), January 19, 2005, page 8D.
^ abMaureen Ryan (with assistance from Mike Conklin. "Reporting live from the land of hats; the case of the outed 'L&O' DA," Chicago Tribune, January 21, 2005, Tempo section, page 1.
^David Zurawik. "'Law and Order' outing, axing character throws fans a curve," The Press of Atlantic City (NJ) (reprinted from The Baltimore Sun), January 24, 2005, page B3: "'A lot of people were really surprised, and a lot of lesbian women were shocked; the comment about being gay seemed to come out of nowhere,' said Sarah Warn, founder and editor of AfterEllen.com, a Web site that reviews media depictions of lesbian and bisexual women. AfterEllen has been running a poll since Thursday asking viewers if they were surprised to learn that 'Southerlyn is gay.'"
^Sarah Warn, quoted by Zurawik, January 24, 2005: "'I think many people in the poll felt like it was a last-minute, cheap stunt that the writers thought up the night before — not something that they have been building up to for four years with the character,' Warn said."
^Ward Triplett. "Stargazing" (column), The Kansas City Star (MO), January 21, 2005, page E2: "Fans of Law & Order are calling it a "cheap stunt" that the character Elisabeth Rohm played wasn't revealed to be a lesbian until she was fired."
^Tim Goodman. "Powell's leaving FCC won't ease our crankiness" San Francisco Chronicle, January 26, 2005, page E1.
^Diane Holloway. "The two most annoying actors on prime time - Shows' popularity doesn't make Caruso or D'Onofrio any less irritating," Austin American-Statesman (TX), February 15, 2005, Lifestyle section, page not listed.
^Kevin D. Thompson. "The best new series! - The stupidest reality shows! The most outrageous scene stealers!" (year-end column), The Palm Beach Post (FL), December 25, 2005, page 1J.
^Alan Sepinwall and Matt Zoller. "Presidential timber - all TV," The Star-Ledger(Newark, NJ), January 24, 2005, Today section, page 35.
^ abRick Kushman. "'West Wing' on welcome upswing," The Sacramento Bee (CA), January 26, 2005, page E1.
^Gary Levin and Robert Bianco. "ABC's 'Housewives' promo remains a hot topic," USA Today, January 24, 2005, page 4D.
^Alan Pergament. "Memorable one-liners from the press tour," The Buffalo News (NY), January 28, 2005, page C5.